Grasshopper

algorithmic modeling for Rhino

# APPROXIMATE VOLUME FOR OPEN POLYSURFACE

Hello Grasshopper users and masters!

I am trying to calculate the volume of existing surface of the field and the road to be constructed.

Actually I am trying to calculate the volume of the filling soil.

However at the end I am ending up with open brep / polysurface.

Can you guys help me how to mend this open polysurface and calculate the volume approximately?

Regards...

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Is this about closing an open polysurface so you can measure the volume, or defining a new volume metric that works on open polysurfaces?

What does the open polysurface look like? I.e. what sort of holes does it have?

Hey David;

The red polysurface is the excavation geometry (roughly).
In the red surface there are many small tiny little openings and i dont know how to fix them one by one.

Yellow is the roads. they are quite smooth and i guess there are no open cavities with them.

What I am trying to do is

1) extrude yellow surface far below the red one

2) trim the yellow surface from the intersection of red.

Then I must end up the FILLING geometry for the road. Im just trying to calculate how much soil needed for the construction.

Results are not need to be precise.

I need some idea how to approach this issue.

Cheers!

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Thanks Tom;

Your tips sparked my mind and I put some of my bricks on yours.
Now the job is done.

Cheers!

If accuracy is not paramount, then a sampling approach may work. You basically shoot thousands of lines from the road surface (use Populate Geometry to generate a good point-spread) downwards until they hit the surface. Since the surface has holes, some lines won't hit it at all, you need to remove these. Then you divide the total road surface area by the number of remaining rays, giving you the average area for each ray. This average area multiplied by the length of the ray gives you the approximate volume per ray. Add up all the approximate volumes for your final answer.

One problem is that the excavation surface is above the roads in certain places. What needs to happen here?

Yeah I know
In some areas the excavation surface is higher than the road.
Such areas must be excavated more.
But they are not too much I simply ignored them.

Incidentally I really wouldn't recommend working in millimetres that far away from the origin. All sorts of mathematical inaccuracies creep in when your numbers are too big.

Ahh yeah you are right
Why i didnt think that.
Sometimes my brain needs a small spark to generate new ideas.

Thanks David

Next time i will keep that in my mind and next time I will fix such things quicker

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Wait, I did it wrong. It's better if you calculate the average are per ray using the original ray count, not the reduced ray count I think.

David,

Is it the filling volume?
It is not a quite realistic figure to me.
My results was around 120 K m³

Also, forgot to mention I converted your geometry to coarse meshes first in Rhino. Seemed like the smart thing to do.

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